In a conventional desk chair, a spring flexibly supports the backrest support on a stationary lower support part. The spring is supported on the lower support part and on an adjustment nut threaded on a tie rod. The tie rod is connected with the backrest support and acts on the spring. The position of the nut on the tie rod can be adjusted only at the front edge of the seat. This type of chair is disclosed in U.S. Pat. No. 2,321,385 to Herold.
A conventional height-adjustable chair, table or the like has a tubular center post with a bottom extended part arranged to slide on or in another similar tubular trunk. The tubular trunk is perpendicular with a base member. A stop member can be inserted through an opening of the wall of the tubular center post between two adjacent spherical fillers. The fillers are found at a distance from the top end of the trunk corresponding to the desired height adjustment. The stop member is formed by a protuberance connected with the bottom of the seat surface which can be flipped up. This type of chair is disclosed in Austrian Pat. No. 264,060.